A hollow cone is built with a small metallic ball free-floating inside. At the narrow end of the cone on the inside of the cone is fixed into place an electromagnet. The electromagnet is turned on and off at regular frequencies. Every time the electromagnet is turned on, the metallic ball, from wherever it is located inside the cone, is attracted to the electromagnet and moves towards the electromagnet. The cone in turn, which is fixed to the electromagnet, is pulled by the electromagnet towards the ball. The motion of the cone forward towards the ball serves as a propulsion for the spacecraft. This does not require a propellant. Every time the electromagnet is turned off, the ball begins to float freely. Since the ball occupies a hollow cone, the ball is more likely to migrate to the wider sections of the cone because of entropy. This produces the distance needed for the next attraction propulsion. Therefore, this is an entropy electromagnetic propulsion system without need of propellant.

I came with the idea for this today. First, has anyone proposed such a propulsion system? Second, would such a propulsion system work? Thirdly, would it be efficient? Lastly, what are the technical details remaining? I'm not a physicist and my math is a bit rusty, so I am asking the members of the forum to give me some help on this. Are there zero-propellant propulsion system currently designed?

The big end of the cone is the front of the engine. Turn on the magnet, the ball moves to the back, taking some time to do so. During this time the spacecraft accumulates momentum and velocity toward the front. Turn the magnet off, the ball strikes the front taking almost no time to jerk to a stop, taking back the momentum, hence velocity imparted to the engine/spacecraft on the "thrust stroke." Then the ball somehow drifts to the front of the engine and the second thrust stroke begins.

So the engine/spacecraft has a small positive forward velocity during the time interval that the ball is being attracted to and moving toward the electromagnet. This velocity integrated over the time interval of the "thrust stroke" results in distance moved. Hence the spacecraft inches along a distance during each "thrust stroke."

Unfortunately, it never builds up any velocity so try it on the ground first.

Every time the electromagnet is turned off, the ball begins to float freely.

No it doesn't. When the magnet is turned off, the ball continues towards the rear of the vehicle with the velocity it has been given by the magnet.

When it hits the vehicle aft wall, it cancels the vehicle's movement forwards and (assuming the ball bounces) both vehicle and ball move in the opposite directions. Then it bounces off the forward wall, etc etc.

A small amount of energy is lost as heat/vibration in each collision, eventually it runs down.

The finally net velocity of the vehicle relative to its starting point is zero. The final distance relative to its starting point is zero.